Hearing loss affects approximately 25 Million Americans. It also affects approximately 35% of those 65 and older. The primary cause of hearing loss in this group is a result of a loss of hair cells. Our interest is in understanding the molecular events that determine hair cell function, and how these events are controlled. We anticipate that such an understanding will allow rational therapies to be developed to treat hair cell loss. Hair cells are the primary transducers of sound serving to convert the mechanical energy of sound to a coded a neuronal one. In this proposal we are seeking to understand the molecular basis of the large conductance potassium channel as it affects hair cell function. Specifically, we are trying to elucidate the molecular determinants of how these channels bring about electrical tuning, a mechanism of frequency discrimination. We are also interested in determining the molecular basis of how they are clustered and co-localized with the voltage gated Ca channel at the basolateral surface of hair cells. The loss of the large conductance potassium channel in mice results in progressive hearing loss. We propose to extend previous work that has identified variations in the primary structure of the protein, and now seek to determine how interacting proteins influence its function. We have already isolated several proteins from the cochlea that interact with a limited portion of this channel using the yeast 2 hybrid technique. We will now determine how these interacting proteins affect the kinetic properties of this channel. We will also determine how these proteins affect it basolateral sorting, clustering and co-localization with voltage gated Ca channels. In addition, we will extend our successful yeast 2 hybrid approach to identify other proteins that interact with entire BK channel. These proteins too will be subject to similar assays. For these experiments we wilt use the chick as a model and will use a modular set of assays that we have developed to test their significance in affecting these physiological processes.